Coil forming method



M. ESAACSQN COIL FORMING METHOD Filed June 20, l95

May 1, 1956 M. lsAAcsoN con. FORMING METHOD 2 Sheets-Sheet 2 Filed June20, 1951 FIE. I3

INVENToR BY i z United Parent O 2,743,508 colL FonMlNG METHOD MaxiIsaacson, Dayton, Ohio, assignor to Globe Industries,

Inc., Dayton, Ohio, a corporation of Ohio -v This invention relates Loan electric motor and to the method land apparatus for manufacturing themotor.

Theproblem of manufacturing motor stators having a plurality of woundfield coils evenly distributed throughout stator slots, in which the`opening into the stator slot is relatively narrow in comparison with thewidth of the main portion of the slot, is particularly pronounced whenmanufacturing stators for miniature aircraft motors of the type in whichthe stators .have an external diameter in the neighborhood of one inch.It is an object of this invention to vsolve this problem in a new andimproved manner by preforming the coils before insertion linto the slotsin such a manner that thepreformed coils may be slid into place from oneend of the stator.

Another object of this invention is to provide a num-A ber of .coilswhich have been preformed in such a manner that the sides of two coilsmay be simultaneously slid into place in a single coil slot withoutinjuring the insulation on the fine wires forming the coils.

`Another object of this invention is to provide an improved coilarrangement and method of manufacturing the coils which makes itpossible to wrap the sides of the coils in insulation before insertingkthe coils in the coil slots.

A further object of this invention is to provide an improved type ofmandrel for -use in winding stator coils.

Still another object of this invention is to provide an improvedconstruction and arrangement which makes it possible to first insert oneseries or set of preformed coils and then insert as second series or setof preformed coils in staggered relationship to said first set of coils.

More particularly, it is an object of this invention to provide amandrel for use informing coils whereby the coils when formed thereonhavea cross sectional configuration at the one end which iscomplementary to the configuration ofthe projected cross sections of thestator slots into which the coils are to be inserted, whereby the coilsthus formed ,may be assembled by sliding the coils into' the slots fromone-end of the motor stator or the laminations formingthe motor-.statormay be individually slid onto the coil assembly.

Still another object of thisinvention is to provide an improvedconstruction and arrangement which facilitates tying strings around thecoils so as to facilitate handling of the ,coils and so asto hold thecoils in proper assembled relationship during and after removal of thesame from the coil winding mandrel;

Another object of this invention is to provide a method and apparatuswhich makes it possibleto form the coils from a skein of wire.

Other objects and advantages reside in the construction of parts, thecombination thereof and the mode of operation, as will become moreapparent from the following description.

vInthedrawing: t p

Figurel is an end yelevational View showing a motor stator having oneset of coils comprising one-half of the stator coils mounted in place;

Figure 2 is a side elevational view showing a motor stator having theone group or set of coils assembled in place and having a second groupor set of coils partially inserted into the stator slots;

Figure 3 is a perspective view of one group of preformed coils;

Figure 4 is a fragmentary sectional view taken substantially on line 4-4of Figure 3 showing the construction of the preformed coils at theleading edge thereof;

Figure 5 is an end view illustrating the construction of the mandrelused in preforming the stator coils;

Figure 6 is a side view of one of the wings forming a part of themandrel;

Figure 7 is a bottom view of the wing shown in Figure 6;

Figure 8 is a fragmentary perspective view of the coil forming mandrel;

Figure 9 is an end view showing a modified type of mandrel for use informing coils;

Figure l0 is a perspective view of a modified mandrel;

Figure 1l is a side elevational view of a modified wing;

Figure l2 is a view picturing one stage of assembly;

Figure 13 is an end elevational view of a motor stator; and

Figure 14 is an end elevational view showing the coils mounted in thestator slots.

Referring now to the drawing wherein I have shown preferred embodimentsof my invention, reference numeral 10 designates a conventionallaminated motor stator having coil slots 12 formed therein, as shown inFigure l. These coil slots are narrowest at the point closest to themotor rotor (not shown) and consequently it is not possible to laypreformed coils directly into the coil slots. For the purposes ofillustrating my invention, l have shown a stator of the type havingeight slots for accommodating eight individual coils 15, each of whichis provided with two sides, so that the sides of two coils are insertedinto each stator slot. Figure l shows a set of four of the coils mountedin place.

While this invention is applicable for use in motors of all sizes, it isparticularly advantageous for use in manufacturing miniature motors ofthe type commonly used in the aircraft industry because of thedifficulty of using ones fingers or any tools for winding the coilsdirectlyv into the stator slots and because of the impossibility oflayingpreformed coils directly into the coil slots. It is very diflcult,if not impossible, to properly wind these miniature motor stators by theuse of the prior art techniques.

By prewinding the coils in a manner to be explained more fullyhereinafter, it is possible to form the coils 15 before they are mountedin the stator slots into such a shape that it is possible to slide thecoils into place from one end of the slots.

In prewinding the coils, one preferably uses a mandrel or fixture of thetype shown in Figures 5, 6, 7 and 8 of the drawing. This mandrelcomprises a central shaft 14 on which there is mounted a longitudinallyslotted cylindrical core 16 to which a plurality of wing-like elements18 are adapted to be removably attached. Each of the wing-like elementsis provided with a projection 20 which fits into one of the slots 22formed in the core 16.

For purposes of illustrating the invention, the fixture illustrated inFigures 5 through 8 has been shown as having eight of the wing-likeelements 18, whereas a four coil assembly of the type shown in Figure 3could be made on a mandrel having only four wing-like elements.

lThe wing-like elements 18 may be held in place on the cylindrical core16 by/any suitable means, such as the screws 19 (see Figure 5) whichproject into tapped recesses 21 in the central core 16.

Figure 9 shows a mandrel having only four wing-like final configurationof the coil assembly.y As best shown v Figures sans 14. By ifrnieorthisconstruction, the Ycross sectional conliguration of the coilsaftthepoin't adjacent the Aporti'oiill is -le'ss than thefprojectedJcross sectional area of the stator slots, with the result that thecoils can befln'sltd erfdwise ilt V`the'. Staforslt's.

Prior to the wndingvoperation, sheets `ofiri'sulaion132 are laidi-nbeti'afeenI the wing members 18; as best shown in Figure 5, so thatWhenltlieil's-'have all been-wound, theywill be wrapped in insulation.IThis Wrapping Eof insulation further protectsthescoils t"asi-they are'inserted into the startor slots. The Ionter edges' 'of 1 the insulation-32 are, of cou-'rsa ben'tfoye'r into #overlapping relationship with thecoil windings before being inserted into 'the motor-'statoi'f- -Asshown'i'rl vFigure 5, Ystrings 34 may -a-'lso be laid in place on themandrelbefore the coil Winding operation and these strings-'inlay `be'used for tying the coils 'together' at ltheends, las best shown `inFigure 3. While I have shown theedges of the `insulation projectingoutwardly fromlthe coilsiots, 'theyfcould be placed underne'athvthewingslszzi and-:then foldedover 'after removal of the wings.Y f f YAfter the wire forming'the coils has been wound onto the mandrel, butybeforeV the wings 18 are removed so vas to release Ithecoi-ls from't'he'rnandreh 'the 'coils -are coated with a fbondingvmaterial iwhichisv.prete'rably. ifnftheform of aninsul'atingvarnishcr lacquer whichservesIto-hold the-coils in theformation "shown in Figure "The coils may bebaked while still on the mandrel -'-6r,fiff"desired, the coating maybeallowed -to partially-dry before being removedfr'om the vf'man'drel and`l'aloed after "being .removed'rom the mandrel Ybut beforerbeinginserted:info the vfst'atorlslots. 5l" he ends 'fof the stringslatfthe leadingend of the coilserve la's convenientfmeans for pulling the coilsiniplace. Y

.'As bestis'hownrin Figure lll-'of thedraw'ng, vvth'erloop portions-fthe I'coils-'aref madellongfenough so as 4'to make itrpossible 'tobendfthe loop portion of'tb'elirls't' set'of c'oils insertedsutiiciently so as to clear the empty statorfslots 12, 'so thatA afterthe fiirst set ofcoils hasfbeen :installed inthe motor -stator slots,the second setfof-.coils "canfbe L inserted without interference fromtherstfset of coils.

Byvirtue of the above described method-and arrangement, it is possibleto manufacture a. `Vstator in which 'a maximum amount fof. copperlrnaterialmay be inserted intofa'miniinum amountfof-coilfslot space. Thecoilfassembly shown in Figure 3 'forms Ian endless ringorfspider whichvwhen impregnatedwith the'fbonding material may be rria'de irigid "so lasto facilitate ha'ndli'ng 'and i installation of the coils. If desired,"the'leoils' i'forrning "the ring or spider "slfiownl inFigure Y3'may'beslid fintoplace directly from the vco'reiof*themandrel 16merelyby llinin'g 4up =the mandrel with the-stator' after removal of thewing members 1li. The'coilassembly,'as-shown infFigur'e 3, somewhatresembles 'a bird Ac'ag'ea'nd maybe thus'designated todistinguish'from'othertypes ofi-'coil Aassemblies wherein each Ycoilisan :independent unitde'tached "from the adjaic'e'ntcoils. Y,

vThe 'bonding materialv which is applied'to the c'il'sprior totheinstallation of' the coils Sin -the motor stator serves to holdthe-coilsin thedesired shape during thesintroducmembers 18a lwhich are'similfa'rfin A'every respect to the wing members 18 describedhereinabove except that the one vend of thewing mer'n'be'rs "terminates,ushwi'tlrthe one end of'the'core 16 as shown 'a't '36.J By yforming thewing membersyas shown 4in "Figure .l0 of the drawing, it is possible towrap the coils by iirst forming the coils into a large skein 38-an'dftlien Wrappin'gt'heskein onto the mandrel so as to form a seriesof loops or coils. In many instances electrical elements, stators orrotors'are provided with a winding which is formed from a skeinor skeinslooped in a certain manner through "the 'slotsof the stators orroto'rs'to'forrnv `a group 'orgroupsbf `A(foils, each -group 'consisting"of aplra'se lbelt. In "thes'e'instances the loops or coils areformedfbypla'cing different sections or parts of a skein 'into'diiierentslots ccodirrgf'to my invention, -a winding 'of-this typemaybe "formed lby nist looping Aor placing J`the V'slzein 'into Jthe'vs'lotsf'of the mandrel shown in'Figure '10.' vAsthe'fsucccedingsections 'of lthe skein are v ]gz'laced into the slots,there lis formed a series of 'coils which constitute one phase-belt inYAaccordance with well vknown practice Each of" tirev coils thirsform'edhas a number of Aseries connected turns, the numberbeing 'equal-to 'thenumber'o'f turns'b'f 'the skein and the series connection' between 'two'turns of `the coil 'being vmade through lthe''remainingportion-vof therespective turns ofthe skein. The 'procedure' of 'placing the skein intoi the "slotsvof vthe Tmandrel shown `iniFigui-'e l0 is the saine as ifthe skein were-placed directly into the slots of a stator. One -or'several skein's,'thatis, va single phase beltor fa completestator'winding, maylthus be placed on themandrel which thereafter isimpregnated' with a bonding material so Vthat upon removalofthe wings18a, v'the coils-will retai-'n thefdesired v-shape so 'that the entireassembly of coils may be inserted endwise-into the stator slots.

While'l havedescribed'an-arrangement -in which "the preassernbledV'coils are slid into #place in 'the Vslots -ofa conventional motory'stator inadeup from a series 'ofpreassembled laminations, 'theprocedure rn-ayv be vv-a'i'cd slightly by performing `'the rcc'ils'andrthen slipping the individual motor stator laminationsiffinto placeo'rl'tthe preformed 'coilsfwhich 'then `'serve :as a mandrel fortassemblingthe statorlllaminations. As best'illustrateiiiin Figuresl2-andl'4', the'prc'formed coils 42lareso-arra1rgetl and shaped-'attireone end-that the cross sectionalfarea of 'the coil assemblysubstant-i'z'rlly con'espon'dsnf shape'to the cross sectional areao'fthe stator slots. fit lwill'bc noted :from viewing Figure 1-4 thatthe'connecting ends of the' coilsiare all disposedfinsuch 'a manner asto `clear ing shaft (not shown) of a motorelfoton'with the lresult thatit is not necesarsy-tolreform or -lbend'flhe -endiportions vof the`coils after Jvthe coils have-'been 'mourl'ted inl out the objects setifo'rth, `as disclosed ,and defined/inthe' appended claims.

Having lthus described Ymy invention, 1I claim;

l. The method of manufacturing a motor-fstatorcom# prising forming astator having longitudinally-:extending coil slots along its inner'periphery,'preforming stator coils 'upon `a mandrel 'seas "to'have 'a'cross :sectional conJ figuration at the one end thereof which iscomplementary to the conguration of the projected cross sections of thestator slots into which the coils are to be inserted, wrapping a sheetof insulating material around the side portions of said coils, coatingthe coils with bonding material, thus making the coils self supporting,removing the coils from the mandrel, and thereafter sliding the wrappedcoils into the stator and into the stator slots from one end of saidstator slots.

2. The method of manufacturing a motor stator co1nprising forming astator having longitudinally extending coil slots arranged along itsinner periphery, preforming stator coils upon a mandrel so as to have across sectional configuration at the one end thereof which iscomplementary to the configuration of the projected cross sections ofthe stator slots into which the coils are to be inserted, impregnatingthe coils with a bonding material so as to retain said configurationduring insertion into the motor stator slots, removing the coils fromthe mandrel, sliding the coils into the slots from one end of saidstator, and thereafter bending end portions of the coils into alignmentwith the solid end wall portion of the stator so as to hold the coils inplace.

3. The method of manufacturing a preformed coil assembly which compriseswinding a plurality of coils about a central axis upon a mandrel withthe sides of adjacent coils arranged in abutting relationship and withthe connecting end portions at the one end of the coils eX- tending in adirection towards the central axis, impregnating the coils with abonding material so as to hold the coils in said relationship forinsertion into a motor stator, removing the coils from the mandrel,followed by endwise insertion of the coils into the stator.

4. The method of manufacturing a motor stator having a multiplicity ofcoils which comprises forming a stator with axially extending coil slotsin its inner surface, preforming coils in a mandrel prior to insertioninto the stator slots with adjacent edges of the coils in abuttingrelationship whereby the coils form an endless ring, impregnating thecoils with a bonding material so as to hold the coils in said ringformation, removing the preformed coils from the mandrel, and thereafterinserting the coils endwise into the stator slots.

5. The method of manufacturing a preformed coil assembly for an elementof an electric train by means of a mandrel having axially extending coilslots which comprises inserting insulating material in said coil slots,winding a plurality of coils into said slots with the sides of adjacentcoils arranged in abutting relationship and with the connecting endportions at the one end of said coils extending in a direction towardsthe central axis, applying a bonding material to the coils while in saidcoil slots, thus retaining the coil contigui-ation, baking the coilassembly, removing the coils from the mandrel, followed by endwiseinsertion of the coils into an element of the electric machine.

6. The method of manufacturing a motor stator comprising forming aplurality of individual stator laminations having coil slots adjacenttheir inner periphery, preforming stator coils upon a mandrel so as tohave a cross sectional configuration at the one end of the coils whichis complementary to the configuration of the projected cross sections ofthe stator slots, applying a bonding material to the coils therebyretaining the formation of the coils, removing the coils from themandrel and thereafter sliding the individual stator laminations endwiseonto said coils.

7. The method of winding stator coils for use in an electric motor whichcomprises producing a skein of conductors, progressively feeding theskein radially into slots of a forming mandrel so as to preform thestator windings, baking the coils in the presence of a bonding andinsulating material, removing the coils from the mandrel and thereafterinserting the coils thus formed endwise into the slots of a motorstator.

8. The method of manufacturing a motor stator having a stator providedwith longitudinally extending internally disposed coil slots by the useof a mandrel having a core removably supporting wing members, the coreand wing members being so shaped that the coils wound thereon have across sectional configuration at one end thereof that is complementaryto the cross section of the stator slots, said method including thesteps of winding coils on said core, applying a material to the coilswhich retains the conguration of the coils, removing the support ingwing members from the core leaving the wound coils intact on the core,aligning the core with the wound coils thereon with the stator slots sothat the sides of the coils register with the slots, and sliding thecoils endwise from the core into the slots to thereby position the coilsas a leld winding in the stator.

References Cited in the iile of this patent UNITED STATES PATENTS706,508 Armstrong Aug. 12, 1902 829,801 Pratt et al. Aug. 28, 19061,365,015 Zwicker Ian. 11, 1921 1,479,285 Cullin Ian. 1, 1924 1,697,134Neely Ian. 1, 1929 1,772,851 Apple Aug. 12, 1930 1,895,427 Steuer et al.Jan. 24, 1933 2,269,678 Mauerer Ian. 13, 1942 2,395,736 Grundmann Feb.26, 1946 2,400,008 Korte May 7, 1946 2,426,090 Gartner Aug. 19, 19472,432,267 Adamson Dec. 9, 1947 2,445,986 Adamson Iuly 27, 1948 2,561,352Ferris et al. July 24, 1951 2,580,293 Gier et al. Dec. 25, 1951 FOREIGNPATENTS 11,729 Great Britain of 1903

